Clearcuts are a completely anthropogenic disturbance, as are the two subsequent chapters on plowed fields and mines. We consider here only disturbances that remove all tree cover or that leave only a few stems to provide seed sources for natural regeneration. Selective cutting is mentioned only if it is compared with clearcuts. Here we cover primarily clearcuts that are not subsequently managed by human intervention because our interest is in spontaneous succession. We also consider cases in which interventions are limited to immediate post-clearcut treatments including burning and chipping of residual materials (logging slash), or, rarely, tilling of the soil, or herbicide use. We excluded studies that used planting or seeding. Slash-and-burn activities in preparation for agricultural activities are mentioned in Chapter 13. Because a substantial biological legacy remains, clearcuts clearly lead to secondary succession.

In this chapter, we present an introductory description of the particular biomes, providing a background to the patterns of succession. Our primary sources for information about the world biomes were Archibold (1995) and Breckle (2002), and for North America, Barbour and Billings (2000). We use the term biome in a broad sense as a widely distributed ecosystem characterized by vegetation with similar life forms and with occurrence, structure, and functioning of the biome largely determined by macroclimate and seasonality.

Mining is an entirely anthropogenic activity that typically removes all biological legacy and therefore initiates a clear example of primary succession. Mines leave as severe a disturbance as do volcanoes, which are at the other end of our natural to anthropogenic disturbance gradient. We consider here succession both in sites where material is extracted (e.g., coal mines, rock quarries, sand and gravel pits) and in sites where material related to mining is deposited (e.g., spoil heaps, dumps, and slurry basins from coal or ore mining). We primarily focus on mine sites (henceforth including extraction and deposition sites) where spontaneous succession has occurred and not on mine sites that have had some anthropogenic amelioration (reclamation, i.e., the return of land to a ‘useful’ purpose; SER, 2004). Typical methods of mine reclamation include leveling the surface, spreading of organic material (including topsoil), the addition of lime (if needed to raise soil pH), and planting or sowing of plant species.

Plant succession is the replacement of plant species and communities over time in response to a disturbance of either natural or human origin. It is a unifying concept of ecology, integrating temporal and spatial scales, abiotic and biotic disturbances, plant-soil and plant-animal interactions, plant life histories, biodiversity patterns, species interactions, and other fundamental ecological principles across a heterogeneous landscape. While we have a simple, intuitive grasp that plant communities change (e.g., abandoned pastures change to forests; vegetation recovers following damaged by fire), the actual drivers of such change are not fully understood, even after more than a century of formal study (Clements, 1916; Glenn-Lewin et al., 1992; Meiners et al., 2015a). One of the challenges is that most work on plant succession (henceforth “succession” because of the preponderance of plant-focused studies; but see heterotrophic succession, Walker & del Moral, 2003) has been specific to a given site or type of disturbance. Yet progress has been made in identifying certain ecological principles that are likely to be important in succession. In this book, we explore global-scale patterns of several key aspects of plant succession to discern at what level generalizations about succession are possible. For the first time, we systematically compare terrestrial successional processes following all major disturbances among all the world’s biomes. This synthesis also provides a framework for aiding land managers attempting to manipulate succession through restoration (Prach & Walker, 2011).

In this chapter, we describe the structure for Part II, where we present a comparative analysis of succession triggered by 10 common types of disturbance in order of increasing human influence (Chapters 5–14): almost no influence (natural: volcanoes, glaciers, cyclones), some influence (intermediate: dunes, landslides, floods, fire), and complete influence (anthropogenic: clearcuts, plowed fields, mines) (Fig. 4.1). Within each disturbance type we cover four topics. First, we describe the disturbance, including what causes it, its spatial patterns, and subsequent disturbances that it might trigger. Second, we discuss the succession that follows that type of disturbance, including abiotic variables (substrate, light, nutrients), biotic variables (biological legacies, dispersal, species colonization and adaptations, the role of invasive alien species, plant-plant interactions, and trophic interactions), and the successional patterns that we found within and among biomes. These patterns resulted from our comparative analyses of multiple studies. Third, we outline several theoretical implications of our findings. Fourth, we address practical implications for management concerns. We end Part II with a brief overview of other anthropogenic disturbances that are not as widespread, frequent, or readily assessed from a successional perspective (Chapter 15).

Volcanoes are the most destructive type of natural disturbance on earth and have been instrumental in the development of continents, mountain ranges, and the destruction of life at global and regional scales. Even today, lava produced by volcanoes is creating new land in Hawaii and other volcanic hotspots. Lava flows that obliterate all previous life are the clearest example of a natural disturbance that initiates primary succession. Initially, there is no available nitrogen or organic matter on a fresh lava flow but other elements (including phosphorus) are present, so when deficiencies are addressed, soils and plant communities can develop. Humans are often drawn to volcanoes because of the rich soils that can result. Indeed, about 12% of all humans live on or within 100 km of an active volcano (“active” in geological terms means erupting within the last 10,000 years) (Small & Neumann, 2001). We start our discussion with volcanic disturbance because it is the least influenced by humans of all disturbance regimes.

In Chapters 5‒14, we discussed 10 widely distributed disturbances and compared successional processes among biomes following each disturbance. We chose disturbances that had been sufficiently studied to permit an analysis of the scientific literature at a global scale. We kept our categories of disturbance as broad as possible to incorporate many related studies. For example, under volcanoes, we included lava, tephra, pyroclastic flows, debris avalanches, and lahars. Under landslides we included slides, flows, and falls of rock, regolith, and sediments. Under mines we included extraction of coal, rock, peat, sand, and the waste piles from these extractions. Yet the complexity of disturbances and their myriad interactions make any categorization somewhat arbitrary and incomplete: arbitrary because one could argue for different categories (e.g., we divided wind damage into dunes and cyclones but pooled all volcanic disturbances and pooled all fire-damaged ecosystems); incomplete because certain disturbances are inevitably left out. For example, under cyclones we did not address individual tree falls; under floods we focused on rivers but did not address flood zones of ocean beaches, lakeshores, or reservoirs; under fire we largely ignored low-intensity fires; while under clearcuts we did not address selective cutting or treatments followed by planting or seeding. Thus, our focus has been on disturbances that were illustrative of general successional principles without attempting a comprehensive review of all terrestrial disturbances.

A floodplain occurs where river water leaves its normal channel and deposits or removes sediments during a flood event (Plate 17). Deposited sediments can be ephemeral because they are subject to erosion from the next high-water event. Yet where floodplains provide a stable surface, plant growth and succession can occur. Substrate texture and fertility vary, much like landslides, and this variability affects succession. The interaction of substrate quality with local topography and water quality and flow create many habitats for plant growth. Floodplains represent (like landslides) an intermediate status between primary and secondary succession. At one extreme, floods can completely remove all prior vegetation and organic matter, triggering primary succession on a layer of fresh silt, sand, or gravel. At the other extreme, intact vegetation and soils can raft down a river to a new location or new silt can simply be layered on top of an existing forest floor, leaving everything intact; both of these would trigger secondary succession. Silt deposition over an existing organic soil resembles succession following volcanic ash deposition (Zobel & Antos, 2009). The spatial scale of a flood is generally positively correlated with its intensity because large floods often provide the most intense, damaging results (Hughes, 1997). Floodplains are also intermediate in their susceptibility to human influence compared to other types of disturbance. Humans have long resided on floodplains, which are fertile and flat, and they provide many services (e.g., for drinking, fishing, washing, cooking, waste disposal, and transportation). Manipulation of floodplains began early in human history (e.g., with irrigation channels for agriculture) and has culminated in vast destruction by humans who have co-opted many floodplains for industries, hydropower, and urban growth (del Moral & Walker, 2007).

Cyclones (also called hurricanes or typhoons) are the first of two types of wind-caused disturbance that we discuss. The second category is dunes, covered in Chapter 8. Cyclones damage forests and infrastructure such as buildings, utility poles, and marinas. Cyclones can also be deadly, particularly in low-lying countries such as Bangladesh, which has lost hundreds of thousands of people to cyclones (Berz, 1988). They are also frequently accompanied by heavy rains, which can trigger flooding and landslides. Cyclones are primarily a disturbance of tropical climates but can also be found in temperate regions; they are most common in the Pacific Ocean, followed by the Indian and Atlantic Oceans (Plate 13).

Fire represents one of the most heterogeneous disturbances that we consider. Fires differ greatly in their intensity, frequency, and spatial extent. We consider here only intense fires where most aboveground biomass is consumed by fire. We focus on succession after a single fire and consider repeated fires as initiating separate seres. However, the frequency of fire in the past and the fire return interval (McKenzie et al., 2011) are important factors that influence the course of succession by altering local and regional species pools (Settele et al., 1996) and local site conditions (Johnstone & Chapin, 2006). Succession in ecosystems that are fire adapted differs from those that are not (Johnson, 1995) because in the former, there are species adapted to either survive the fire in situ or easily colonize the site immediately after the fire. Ecosystem adaptations to fires can occur over millions of years (Korasidis et al., 2016). Post-fire succession is usually considered as a type of secondary succession (Walker & del Moral, 2003), but in the case of highly intense fires where all biological components, including litter and humus layer, are burned, the recovery approaches primary succession.

Dunes, like cyclones, are disturbances caused by wind and only partially affected by humans. Unlike cyclones, which leave soil intact, dunes bury the soil in sand, thereby initiating primary succession. Dune formation can be triggered by such human activities as diversion of lakes or rivers, removal of vegetation by logging or overgrazing, and climate warming that increases aridity and leads to dry surface soil.

In this chapter, we consider situations in which plowed fields are left without cultivation following growth of a final crop. The crop is usually harvested but sometimes is left in place and may provide some legacy from the previous use and influence subsequent succession. Thus, succession usually starts on bare ground but with an agricultural (weedy) seed bank present, and with developed soil, though the soil is sometimes degraded by intensive use. Consequently, plowed fields represent clear examples of secondary succession (Burrows, 1990). Other terms for unused plowed fields include abandoned fields, fallows, or old fields (Cramer & Hobbs, 2007).

Succession is a natural process of ecosystem development following a disturbance. In this chapter, we review basic theoretical concepts concerning succession and examine how humans have interacted with it. We document how human approaches to environmental change gradually became more formalized as a study of succession, a study that is now a dynamic tenet of ecology. We end the chapter with a discussion of how succession is currently studied.